Data race condition

The value of the shared data will be determined by the interleaving of thread execution. Thread shared data is accessed without holding an appropriate lock, possibly causing a race condition
/src/mongo/db/repl/oplog_buffer_blocking_queue.cpp:67: MISSING_LOCK 169224 Accessing "this->_drainMode" without holding lock "mongo::repl::OplogBufferBlockingQueue._notEmptyMutex". Elsewhere, "mongo::repl::OplogBufferBlockingQueue._drainMode" is written to with "OplogBufferBlockingQueue._notEmptyMutex" held 2 out of 2 times (2 of these accesses strongly imply that it is necessary).